1. Field of the Invention
The present invention relates to a recording apparatus for high-speed beam recording of image information such as characters and graphics supplied from a computer or a facsimile transmitter, and more particularly to a recording apparatus for information recording by periodically changing the scanning direction of said beam.
2. Description of the Prior Art
With the recent development of computers there have been desired high-speed and high-quality output apparatus for image information such as characters and graphics. As the high-speed output apparatus principally for character information there are conventionally known a mechanical impact line printer of drum type, a multistilus electrostatic printer, a cathode ray tube printer composed of a combination of a cathode ray tube (principally an optical fiber tube) and the electrophotographic process.
The mechanical impact line printer, however, is associated with the drawbacks of limitation in speed, noise, poor reliability etc.
Also the multistylus electrostatic printer has a limitation in resolution, and requires expensive electrostatic recording paper. Further, the cathode ray tube (CRT) printer is difficult to maintain a high print quality for a prolonged period because of the stability of the CRT drive circuit and also requires a very large volume for the entire apparatus because of the presence of bulky cathode ray tube. Consequently the conventional output apparatus for characters and graphics have not been satisfactory, particularly for characters requiring a high quality such as Chinese characters. Also as the apparatus for the output principally of graphic information there have conventionally known a mechanical X-Y plotter, a drafter, a multistilus electrostatic plotter, a CRT plotter for optically recording a graphic information displayed on a cathode ray tube. However the mechanical X-Y plotter and drafter are very slow in the recording speed while the multistylus electrostatic plotter is disadvantageous because of low resolution, use of special recording paper and its expensiveness, and the CRT plotter is associated with the drawbacks resulting from the low resolution, poor stability and insufficient light intensity of cathode ray tube itself.
In order to eliminate the above-mentioned drawbacks there have been proposed, as disclosed for example in the U.S. Pat. No. 3,971,044 and the U.S. Pat. No. 4,059,833 assigned to the assignee of the present application, recording apparatus in which a beam such as a laser beam modulated by the signal to be recorded is deflected to scan a recording member thereby achieving a high-speed recording on said member. Such recording apparatus, wherein beam deflection being achieved by a rotary polygonal mirror of an elevated mass, requires a large beam deflecting mechanism, thus resulting in a large and expensive device. Also in such case there is required a certain time for the start-up of the recording apparatus as said polygonal mirror has to be accelerated to a predetermined high speed.